Table 1. — Exploratory tests of the guiding effectiveness of 

 six methods of energizing an electrode array. 



Pulsed D.C. and a control should be used in 

 the main experiment, Alternate Polarity was 

 a better test of polarity than Pulsed D.C; 

 therefore, we omitted the latter. 



Guiding effectiveness indicated by the ratio of the 

 number of fish in the narrow channel to the total 

 number recovered downstream, expressed as a percentage. 

 A comparison is made between treatment and control by 

 taking the deference between the percentage of each. 

 This difference is called index of effectiveness. 



A.C. was unpromising. The percentage of 

 fish recovered in the narrow channel was the 

 lowest for this condition cind was actually 

 less than that obtained with the control 

 condition. Because there were numerous dis- 

 tressed and several dead fish in some of the 

 A.C. explorations not listed, A.C. was elim- 

 inated from further tests in this series. 



D.C. also did not appear to yield 

 satisfactory results. In the first set of 

 experiments, the effectiveness, as indicated 

 by the percentage in the narrow channel, was 

 intermediate between A.C. and the four types 

 of Pulsed D.C, although more than twice the 

 index in the control. In the second set, 

 there was no apparent difference between the 

 treatment and the control. Because of the 

 apparent low effectiveness and because there 

 were some distressed fish and some dead 

 fish, D.C. was not considered for further 

 use in the series. 



We used sequential energizing with 

 positive polarity both upstream and down- 

 stream. These two, with Alternate Polarity 

 and Pulsed D.C. were similar in guiding 

 effectiveness in both sets of explorations. 

 In the small number of trials in the first 

 set, there was a difference between Alter- 

 nate Polarity and Positive Upstream, but 

 this was not the case in the second set. 

 Although it appeared that the four types of 



THE EXPERIMENT 



The main experiment was designed to 

 test the relation of field polarity to the 

 fish-guiding effectiveness of a sequentially 

 energized single-row electrode array. It 

 was also designed to obtain a measure of the 

 extent of variability due to sample size in 

 tests of this type. This was accomplished 

 by the use of three types of energized 

 arrays aJid a nonenergized array for control 

 and by the use of three different sample 

 sizes. 



The two sequentially energized arrays 

 were those described previously (fig. 4); 

 fish moving downstream with the water cur- 

 rent were subjected to electrical fields of 

 different polarities. The other type of 

 array was the Alternate Polarity type 

 (fig. 3) and, as the direction of the field 

 reversed at every pulse, any orientative 

 effect due to electrotsLxis was canceled. 



Experiments, conducted on 12 nonconse- 

 cutive days, included a series of 12 tests 

 each day.. The order of testing was varied 

 from day to day to minimize any possible 

 differences due to the time of day or se- 

 quence of tests. Fish were released in lots 

 of 15, 50, and 100 so that the influence of 

 saunple size could be measured. For each 

 size lot, a control (power off) was run. 

 On each of the 12 days 660 fish were used, 

 a total of 7,920 fish. The stock of experi- 

 mental fish approximated only 4,000 fish, 

 but because the tests extended over several 

 weeks the fish were rested for a minimum of 

 12 days before a second use. With few 

 exceptions, a minimum of 70 percent of each 

 lot introduced moved downstream and were 

 trapped in each 5-minute interval. The 

 results are based on the recovery of 6,237 

 fish which entered the experimental field. 



The numbers of fish and percentages 

 recovered in the narrow channel are trcins- 

 formed by the arc sine method and the anal- 

 ysis of variance was used to determine 

 whether differences existed (Snedecor 1950). 

 The detailed data, trainsformation, and part 

 of the statistical analyses are presented 

 in the appendix. 



